java程序：set改造成map

逻辑：

set是无序不重复数据元素的集合。

map是另一种set，如果将<key,value>看成一个整体的话，其实就是set。在map中，若用map的keyset()方法将key提取出来，便构成了一个set集合。

所以，就定义一个整体SimpleEntry<K,V>作为元素存入set。

代码：

/*

*SimpleEntry<K,V>作为map对象的存储元素

*/

class SimpleEntry<K, V>
implements Map.Entry<K, V>, Serializable
{

// map中的key不可变
private final K key;
private V value;

public SimpleEntry(K paramK, V paramV)
{
this.key = paramK;
this.value = paramV;
}

 

public SimpleEntry(Map.Entry<? extends K, ? extends V> paramEntry)
{
this.key = paramEntry.getKey();
this.value = paramEntry.getValue();
}

public K getKey()
{
return this.key;
}

public V getValue()
{
return this.value;
}

public V setValue(V paramV)
{
Object localObject = this.value;
this.value = paramV;
return localObject;
}

public boolean equals(Object paramObject)
{
if (paramObject == this)
{
return true;
}
if (paramObject.getClass() == SimpleEntry.class)
{
SimpleEntry localSimpleEntry = (SimpleEntry)paramObject;
return localSimpleEntry.getKey().equals(getKey());
}
return false;
}

public int hashCode()
{
return this.key == null ? 0 : this.key.hashCode();
}

public String toString()
{
return this.key + “=” + this.value;
}
}

 

/*

*Set2Map<K, V>继承自hashset，底层是利用hashset来存储，但存储的是<K，V>这样的二元组，所以可以看成是一个map

*/

public class Set2Map<K, V> extends HashSet<SimpleEntry<K, V>>
{
public void clear()
{
super.clear();
}

public boolean containsKey(K paramK)
{
return super.contains(new SimpleEntry(paramK, null));
}

boolean containsValue(Object paramObject)
{
for (SimpleEntry localSimpleEntry : this)
{
if (localSimpleEntry.getValue().equals(paramObject))
{
return true;
}
}
return false;
}

public V get(Object paramObject)
{
for (SimpleEntry localSimpleEntry : this)
{
if (localSimpleEntry.getKey().equals(paramObject))
{
return localSimpleEntry.getValue();
}
}
return null;
}

public V put(K paramK, V paramV)
{
add(new SimpleEntry(paramK, paramV));
return paramV;
}

 

//内部用了迭代器实现

public void putAll(Map<? extends K, ? extends V> paramMap)
{
for (Iterator localIterator = paramMap.keySet().iterator(); localIterator.hasNext(); ) { Object localObject = localIterator.next();

add(new SimpleEntry(localObject, paramMap.get(localObject)));
}
}

//内部用了迭代器实现

public V removeEntry(Object paramObject)
{
Iterator localIterator = iterator();
while (localIterator.hasNext())
{
SimpleEntry localSimpleEntry = (SimpleEntry)localIterator.next();
if (localSimpleEntry.getKey().equals(paramObject))
{
Object localObject = localSimpleEntry.getValue();
localIterator.remove();
return localObject;
}
}
return null;
}

public int size()
{
return super.size();
}
}

 

测试程序：

public class Set2MapTest
{
public static void main(String[] paramArrayOfString)
{
Set2Map localSet2Map = new Set2Map();

localSet2Map.put(“语文”, Integer.valueOf(89));
localSet2Map.put(“数学”, Integer.valueOf(83));
localSet2Map.put(“英文”, Integer.valueOf(80));
System.out.println(localSet2Map);

System.out.println(localSet2Map.size());
localSet2Map.removeEntry(“数学”);
System.out.println(“删除key为\”数学\”的Entry之后：” + localSet2Map);

System.out.println(“语文成绩：” + localSet2Map.get(“语文”));

System.out.println(“是否包含\”英文\”key :” + localSet2Map.containsKey(“英文”));

System.out.println(“是否包含 82 value :” + localSet2Map.containsValue(Integer.valueOf(82)));

localSet2Map.clear();
System.out.println(“执行clear()方法之后的集合：” + localSet2Map);
}
}